Problem: $6c + 9d + 9e - 1 = 7d - 9e - 3$ Solve for $c$.
Combine constant terms on the right. $6c + 9d + 9e - {1} = 7d - 9e - {3}$ $6c + 9d + 9e = 7d - 9e - {2}$ Combine $e$ terms on the right. $6c + 9d + {9e} = 7d - {9e} - 2$ $6c + 9d = 7d - {18e} - 2$ Combine $d$ terms on the right. $6c + {9d} = {7d} - 18e - 2$ $6c = -{2d} - 18e - 2$ Isolate $c$ ${6}c = -2d - 18e - 2$ $c = \dfrac{ -2d - 18e - 2 }{ {6} }$ All of these terms are divisible by $2$ $c = \dfrac{ -{1}d - {9}e - {1} }{ {3} }$